Method of manufacturing crystalline material from different materials

ABSTRACT

A method of manufacturing a crystalline layer of material on a surface, the crystalline layer including lithium, at least one transition metal and at least one counter-ion. The method includes the following steps: generating a plasma using a remote plasma generator, plasma sputtering material from a first target including lithium onto a surface of or supported by a substrate, there being at least a first plume corresponding to trajectories of particles from the first target onto the surface, and plasma sputtering material from a second target including at least one transition metal onto the surface, there being at least a second plume corresponding to trajectories of particles from the second target onto the surface. The first target is positioned to be non-parallel with the second target, the first plume and the second plume converge at a region proximate to the surface of or supported by the substrate, and the crystalline layer is formed on the surface at the region.

BACKGROUND OF THE INVENTION

The present invention concerns a method of manufacturing a layer ofcrystalline material on a surface. More particularly, but notexclusively, this invention concerns making a crystalline layercomprising lithium, at least one different metal and at least onecounter-ion, using a plasma deposition process.

Plasma deposition systems are widely used in a range of industries, fromelectronic device manufacture to the production of hardwearing coatings.In the electronic device sector, there are a number of establishedplasma deposition technologies.

Forming a crystalline layer of material comprising lithium, at least onedifferent metal and at least one counter-ion, using a plasma depositionprocess typically requires an annealing step.

Traditional magnetron sputtering techniques typically suffer frominefficient and non-uniform target utilisation. JP2008045213 is anexample of the proposed use of a pulsed DC magnetron sputtering seekingto achieve a uniform plasma density over a relatively small target area.The method includes pre-heating a substrate to 200° C. and then applyingpulsed DC power to a single sputter target containing LiCoO₂. A layer ofmaterial is formed on the substrate and a rapid heat anneal process isperformed for a short time, in order to form the crystalline layers ofLiCoO₂ with the desired crystal structure.

PCT publication WO2011/131921A1 discloses a method of using a remotelygenerated plasma, and confining said plasma onto the target in such away that there is uniform sputtering of the target material.

However, WO2011/131921A1 is not concerned with the deposition orcreation of crystalline thin-films. It does not discuss, or anticipate,a method of how to deposit a crystalline film in situ throughmanipulation of certain parameters of a thin film deposition system thatutilises a remotely generated plasma. Additionally, WO2011/131921A1 doesnot discuss an apparatus or method that allows for achieving a desiredstoichiometry between target material and the material formed throughsputter deposition of said material.

Whilst the techniques that comprise the state of the art are capable ofproducing thin films of high quality material, there remains a long feltneed for an ability to produce crystalline films of highly orderedmaterial, such as layered oxide materials, at a high rate, with adesired stoichiometry, and utilising target material efficiently.

The present invention seeks to mitigate one or more of theabove-mentioned problems. Alternatively or additionally, the presentinvention seeks to provide an improved method of forming a crystallinelayer on a surface of or on a substrate.

SUMMARY OF THE INVENTION

There is provided according to a first aspect of the present invention amethod of forming a crystalline layer on a surface of or supported by asubstrate, the crystalline layer comprising lithium, at least onedifferent metal and a counter-ion. The method comprises using plasma tosputter material from various targets onto the substrate. A first targetassembly consists of one or more targets each comprising lithium. Asecond target assembly consists of one or more targets, each comprisinga different metal from lithium, for example a transition metal. Plasmais generated using a remote plasma generator. Plasma is preferablygenerated remotely from the first target assembly and remotely from thesecond target assembly. The method includes sputtering material, withthe use of the plasma, from both the first and second target assembliesonto a surface of or supported by a substrate. There is a first plumecorresponding to the trajectories of particles from the first targetassembly onto the surface and there is a second plume corresponding tothe trajectories of particles from the second target assembly onto thesurface. The first target assembly is positioned to be non-parallel withthe second target assembly. For example, it may be that theplasma-facing surface of the first target is planar and theplasma-facing surface of the second target is planar, and that thenormal axes of the planes of such planar surfaces of the first andsecond targets are non-parallel. For example, such normal axes mayconverge towards each other in a direction towards the surface of orsupported by the substrate. It may be the case that, at least for across-section that includes sections of the first target assembly, thesecond target assembly and the substrate, the first target assembly ispositioned to be non-parallel with the second target assembly. Thecross-section referred to may for example be across a plane that isaligned with the length of the substrate and/or perpendicular to theplasma facing surfaces of one or more of the targets. The first plumeand the second plume converge at a region proximate to the surface of orsupported by the substrate, at least as viewed in the cross-sectionreferred to above. A crystalline layer is formed on the surface at saidregion. The counter-ions of the crystalline material may be provided ingaseous form. The counter-ions may for example comprise oxygen.

Embodiments of the method according to this first aspect of theinvention can be used to manufacture multi-element crystalline materialin situ on the surface. The crystalline material may have a structurewhich provides excellent lithium ion mobility and thus suitable forforming cathode material for energy cells in lithium ion batteries, forexample. (While mention is made of batteries herein, it will beunderstood that the invention may have application in other products ordevices which might benefit from the use or inclusion of crystallinematerial comprising lithium atoms/ions). The method of the inventionenables such results by a combination of the use of remote plasma, theuse of different targets for the different elements that are required inthe final crystalline material and the geometry of the system. Theplasma preferably comprises argon ions. A remotely generated plasmaallows for control of plasma energy independently of the targets. Highenergy plasma can be generated, confined and controlled withoutinteraction with any of the targets, in contrast with prior arttechniques which may purely rely on target biasing to generate plasma atthe targets. Sputtering may be achieved by applying a negative,accelerating voltage to the target (referred to herein alternatively as“bias power”), which accelerates plasma ions towards and into thetarget, generating energised ions to sputter from the target. Thesputter threshold (the plasma energy at which sputtering starts) dependson the target material. In general terms, the bias power applieddictates the accelerating field for ions in the plasma and hence theirbombardment energy and therefore the amount of material sputtered.Elemental lithium material typically has a lower sputter yield asmeasured in atoms yielded per ion received at the surface at a givenenergy than transition metals such as cobalt.

Thus, the use of remotely generated plasma distinguishes the plasmageneration process and the sputtering processes allowing the kineticenergy of the sputtered material to be finely controlled, on a pertarget basis for example.

The size and geometry of the targets, the configuration of the multipletargets relative to each other, and the magnetic and electric fields inthe vicinity affects the geometry of the plumes, and their concentrationof charged ions.

The geometry of the plumes and how they mix and converge affects thestoichiometry of the material deposited at the surface. Angling thetargets relative to each other and to the substrate assists incontrolling the plume geometry and therefore the stoichiometry of thematerial deposited.

The proportion of counter-ions relative to the proportion of lithiumions can be controlled independently by means, for example when thecounter-ions are generated by means of the plasma ionising a gas, bycontrolling the flow of such gas into the plasma.

Furthermore, the provision of a system/method in which such separateprocess parameters can be controlled and/or configured independently ofeach other facilitates the deposition of crystalline material of thedesired stoichiometry and having the desired crystalline phase.

In embodiments of the invention, material is deposited directly onto thesurface of or supported by the substrate so that crystalline material isformed in situ as the material is deposited. Crystalline material maythus be formed directly with substantially no annealing step beingrequired.

At least a portion of, and optionally all of, the deposited material mayhave a hexagonal crystal structure. At least a portion of and optionallyall the deposited material may have a crystalline “layered oxide”structure. Such “layered oxide” structures are important whenmanufacturing solid-state batteries, such as for example lithium ionbatteries. A layered oxide structure allows for lithium ions to moreeasily de-intercalate from the crystal structure, resulting in a fastercharging, higher capacity solid-state battery. It may also assist withmaintain a stable crystal structure when the lithium ions have migratedout.

It will be understood that intercalation refers to a property of amaterial that allows ions to readily move in and out of the materialwithout the material changing its phase (chemical and crystallinestructure). For example, a solid-state intercalation film remains in asolid state during discharging and charging of an energy-storage device.

According to the invention, the crystalline material formed on thesurface comprises lithium, at least one different metal and at least onecounter-ion. The crystalline material may be in the form of a layeredoxide structure (or framework), defined by the formula LiBO₂, where B isthe different metal and the oxide is formed from said at least onecounter-ion. The different metal (“B”) may be one or more redox activetransition metals, one or more transition metals or a mixture thereof.Elemental metals in the so called “post-transition metals” group such asaluminium, can also be incorporated into layered oxide frameworks. Thedifferent metal may comprise one or more of Fe, Co, Mn, Ni, Ti, Nb, Al,and V. Cobalt is a preferred choice, for example producing crystallineLiCoO₂.

In the case where the material deposited is LiCoO₂, the material isoptionally deposited with a hexagonal and/or rhombohedral latticestructure, optionally having a form which is in the R3m space group(also referred to as the “R 3(bar) 2/m” space group or space group 166).This structure has a number of benefits, such as having a high usablecapacity and high speed of charging and discharging compared to the lowenergy structure of LiCoO₂, which has a structure in the Fd3m spacegroup (a face centred cubic structure). The R3m space group is regardedas having better performance in typical battery applications due toenhanced reversibility and fewer structural changes on lithiumintercalation and de-intercalation. Therefore crystalline LiCoO₂ in theR3m space group is favoured for solid state battery applications.

During performance of the method, crystalline material may growsubstantially epitaxially from the surface on or supported by thesubstrate. Epitaxial growth is favoured as it allows for lithium ions tointercalate and de-intercalate more easily. In the case where thematerial is LiCoO₂, the crystals are optionally aligned with the (101)and (110) planes substantially parallel to the substrate. This isbeneficial as it means that the ion channels of the thin film areorientated perpendicular to the substrate, making for easierintercalation and de-intercalation of the ions from the battery. Thisimproves the working capacity and the speed of charging of the battery.

Embodiments of the invention may be used to deposit crystalline materialof the general formula Li_(a)M1_(b)M2_(c)O₂, wherein the amount ofLithium, “a” is from 0.5 to 1.5 (optionally 1), M1 is one or moretransition metals (optionally one or more of cobalt, iron, nickel,niobium, manganese, titanium, and vanadium), b being the total oftransition metal, and M2 is, for example, aluminium, with c being thetotal of M2 (optionally zero). Optionally, a is 1, b is 1, and c is 0.Optionally, M1 is one of cobalt, nickel, vanadium, niobium andmanganese.

Optionally, a is more than 1—such materials are sometimes known as“lithium-rich” materials. Such lithium-rich materials may be

${Li}_{({\frac{4}{3} - \frac{2x}{3}})}{Ni}_{x}{Mn}_{({\frac{2}{3} - \frac{x}{3}})}O_{2}$

with x=0, 0.06, 0.12, 0.2, 0.3 and 0.4, for example.

Another such material is

${Li}_{({\frac{4}{3} - \frac{y}{3}})}{Co}_{y}{Mn}_{({\frac{2}{3} - \frac{2y}{3}})}O_{2}$

wherein y has a value greater than 0.12 and equal to or less than 0.4.

Another such material is

${Li}_{({\frac{4}{3} - \frac{2x}{3} - \frac{y}{3}})}{Ni}_{x}{Co}_{y}{Mn}_{({\frac{2}{3} - \frac{x}{3} - \frac{2y}{3}})}O_{2}$

wherein x has a value equal to or greater than 0.175 and equal to orless than 0.325; and y has a value equal to or greater than 0.05 andequal to or less than 0.35.

${Li}_{({\frac{4}{3} - \frac{2x}{3} - \frac{y}{3} - \frac{z}{3}})}{Ni}_{x}{Co}_{y}{Al}_{z}{Mn}_{({\frac{2}{3} - \frac{x}{3} - \frac{2y}{3} - \frac{2z}{3}})}O_{2}$

is another such material, wherein x is equal to or greater than 0 andequal to or less than 0.4; y is equal to or greater than 0.1 and equalto or less than 0.4; and z is equal to or greater than 0.02 and equal toor less than 0.3.

It may be that all lithium targets are considered to belong to the firsttarget assembly. It that may be that all targets comprising the samedifferent metal (or alternatively any non-lithium metal targets) areconsidered to belong to the second target assembly. There may optionallybe a third target assembly consisting of one or more targets, eachcomprising a metal different from those of the targets of the first andsecond target assemblies.

As mentioned above, elemental lithium material typically has arelatively low sputter yield as measured in atoms yielded per ionreceived at the surface at a given energy in comparison to other metals.It may for example be the case that more plasma energy is received atthe target(s) of the first target assembly than at the target(s) of thesecond target assembly, for a given area—for example when the targetsare comparably sized. It may be that more plasma energy is received atthe target(s) of the first target assembly than at the target(s) of thesecond target assembly, per target. It may be that, when viewed in thesame cross-section as mentioned above, the sum plasma energy received atall of the targets, for the 1 mm strip of targets 0.5 mm to either sideof the cross-section, is greater for the target(s) of the first targetassembly than for the target(s) of the second target assembly.

The targets may be arranged in pairs, one target of the pair belongingto the first target assembly and the other target of the pair belongingto the second target assembly.

It may be that more plasma energy is received at the targets of thefirst target assembly (targets comprising lithium) than at the targetsof the second target assembly (targets comprising at least onetransition metal), as a result for example of being biased differently.Additionally of alternatively, it may be as a result, for example, ofthe first target assembly being exposed to more of the the plasma to agreater degree than the second target assembly. The first targetassembly may on average be closer to the region in the plasma of highestenergy than the second target assembly. The target of the first targetassembly closest to the region in the plasma of highest energy may becloser to that region than the target of the second target assembly thatclosest to the region of highest energy.

It may be that the target(s) of the second target assembly are, for anygiven cross-section section taken across the majority of the width ofthe plasma, angled differently to the horizontal, as compared with thetarget(s) of the first target assembly.

One or more target(s) of the first target assembly may comprise adistinct region of elemental lithium. One or more target(s) of thesecond target assembly may comprise a distinct region of elementalmaterial, for example a distinct region of elemental cobalt. A “distinctregion” can mean either its own target, or an area of a target. Theremay be a composite target body comprising multiple distinct regions ofdifferent materials. Such a composite target body can thus includetargets of both the first target assembly and the second targetassembly.

It may be that a target of the first target assembly faces towards thesubstrate in a first direction. The direction may be considered as thenormal of the surface at the middle of the surface of the target thatfaces the substrate, in use. An adjacent target of the second targetassembly may face towards the substrate in a second direction. It ispreferred that the first and second directions converge towards thesubstrate, as this may aid control over the convergence of the plumes.In the cross-section (the above-mentioned cross-section that includessections of the first target assembly, the second target assembly andthe substrate) there may be a first notional line, which is parallel tothe first direction, and which extends from the centre of the surface ofthe target of the first target assembly. In the same cross-section,there may be a second notional line, which is parallel to the seconddirection, and which extends from the centre of the surface of thetarget of the second target assembly. It is preferred that the firstnotional line intersects the second notional line at a location closerto the substrate than to either of the targets. In certain embodimentsof the invention, the directions in which the targets face (when viewedin cross-section) converge towards the substrate/surface and cross eachother at a location that is closer to the substrate/surface than toeither target. The location of the intersection may be further from thetargets than from the substrate. For example, it may be at a location onthe other side of the substrate from the target(s) (in the case that allsuch targets are on the same side of the substrate). In such a case, itmay also be that the location of the intersection is closer to thesubstrate than half of the shortest distance from either of the targetsto the substrate.

The surfaces facing the substrate of the target(s) of the first targetassembly may be planar. In some embodiments the surfaces facing thesubstrate of the target(s) of the first target assembly may be curved,for example being either convex or concave. The surfaces facing thesubstrate of the target(s) of the second target assembly may be planar.In some embodiments the surfaces facing the substrate of the target(s)of the second target assembly may be curved, for example being eitherconvex or concave.

The term substrate as used herein include any structure having anexposed surface onto which a film or layer is deposited, for example, toform an energy-storage device. The term substrate is understood toinclude semiconductor wafers, plastic film, metal foil, thin glass, micaor a poly imide material, and other structures on which anenergy-storage device may be fabricated according to descriptionprovided in this disclosure. The term substrate is also used to refer tostructures during processing that include other layers that have beenfabricated thereupon. Substrates may include doped and un-dopedsemiconductors, epitaxial semiconductor layers supported by a basesemiconductor or insulators, as well as other semiconductor structureswell known to one skilled in the art. Substrate is also used herein asdescribing any starting material that is useable with the fabricationmethod as described in this disclosure.

Material may be deposited simultaneously or sequentially, on oppositesides of the substrate.

The substrate may be flexible. The substrate may comprise a polymermaterial, for example a polymer substrate film having a thickness offrom 0.5 to 10 μm. The substrate may comprise a polymer support. Asupport typically acts to mechanically support the other components ofthe substrate, if any such components are present, and help it resisttensile and shear stresses. The substrate may comprises polyethyleneterephthalate (PET), or polyethylene naphthalate (PEN). PEN and PET arereasonably flexible, and relatively high tensile strength due to theirsemi-crystalline structure.

The method may comprise depositing sputtered material on a first portionof substrate, thereby forming crystalline material on the first portionof the substrate. The method may also comprise subsequently moving thesubstrate, and depositing sputtered material on a second portion ofsubstrate, thereby forming crystalline material on the second portion ofthe substrate. The substrate may be stationary for some of the timeduring which material is deposited onto it.

At least one of the substrate and the first and second target assembliesmay be moving as crystalline layer is being formed on the surface. Forexample, the substrate may be continuously moving while material isbeing deposited onto it. The substrate may be moving relative to thetarget assemblies when the crystalline layer is formed on the substrate.The targets may additionally move. The targets may move slower than thesubstrate, so that the substrate also moves relative to the targets. Theplumes of particles may sweep over the surface on or supported by thesubstrate.

The substrate may comprise, or be in the form of, a sheet, optionally anelongate sheet. Such a sheet may be provided in the form of a roll. Thisfacilitates simple storage and handling of the substrate. The substratemay comprise, or be in the form of, a sheet, optionally an elongatesheet. Such a sheet may be provided in the form of a roll. Thisfacilitates simple storage and handling of the substrate. Alternatively,the substrate may be supplied in discrete sheets that are handled andstored in relatively flat sheets. The substrate may be planar in shapeas the material is deposited thereon. This may be the case, when thesubstrate is provided in the form of discrete sheets, not beingtransferred to or from a roll. The sheets may each be mounted on acarrier, having greater structural rigidity. This may allow for thinnersubstrates to be used than in the case of substrate film held on aroller.

The substrate may be movably mounted to facilitate movement of thesubstrate (optionally in the form of a sheet). The substrate may bemounted in a roll-to-roll arrangement. Substrate upstream of the plasmadeposition process may be held on a roller or drum. Substrate downstreamof the plasma deposition process may be held on a roller or drum. Thisfacilitates simple and rapid handling of flexible sheets of substrate. Ashutter may be provided to allow for a portion of the substrate to beexposed to the remotely generated plasma.

At least part of the substrate may be carried by a rotating drum. Themethod may include a step of unrolling the substrate from a roll ofmaterial, and a step of conveying the substrate to a location at whichthe sputter deposition technique is performed.

The substrate may be curved in shape as the material is depositedthereon. This may be the case, when the substrate is in the form a rollof material, carried by a roller or is otherwise transferred to or froma roll. In the same cross section as mentioned before, the substrate mayhave a radius of curvature at the region at which the first plume andthe second plume converge. It may be that the targets are arrangedcircumferentially around the substrate, preferably around a centre ofsuch a radius of curvature of the substrate.

The substrate may have a width and a length, the length being longerthan the width. The afore-mentioned cross-section may be perpendicularto the width and/or may be parallel to the length of the substrate.There may be a step of conveying the substrate along a predefined path,the path being non-parallel with the width of the substrate. The pathmay be curved, at least in part. The substrate may be in the form of asheet of material, for example conveyed at least in part along thepredefined path by one or more rollers. The substrate may be supportedby a drum when the crystalline layer is formed on the substrate.

The conveying of the substrate along the predefined path may occur whilethe material is sputtered onto the substrate from the targets. Thepredefined path may be able to be defined by a line which is containedwithin the plane of the cross-section.

The substrate may be movably mounted to facilitate movement of thesubstrate. The substrate may be mounted in a roll-to-roll arrangement.Substrate upstream of the plasma deposition process may be held on aroller or a drum. Substrate downstream of the plasma deposition processmay be held on a roller or a drum. This facilitates simple and rapidhandling of elongate flexible sheets of substrate. A shutter may beprovided to allow for a portion of the substrate to be exposed to theremotely generated plasma.

The use of a roll-to-roll arrangement has a number of possible benefits.It facilitates a high material throughput and allows a large cathodearea to be deposited on one large substrate, though a series ofdepositions at a first portion of the substrate, followed by a secondportion of the substrate, and so on. One of the main benefits of aroll-to-roll processing is that it allows for a number of depositions tooccur without breaking vacuum. This saves both time and energy comparedto systems in which the chamber needs to be taken to back up toatmospheric pressure from vacuum after deposition, in order to load anew substrate.

The plasma deposition process optionally takes place in a chamber. Theupstream drum or roller for carrying the substrate may be located insideor outside the chamber. The downstream drum or roller for carrying thesubstrate may be located inside or outside the chamber.

The substrate may optionally not exceed its temperature corrected yieldstrength at any point as it passes between the upstream and downstreamrollers or drums. This is important as roll-to-roll processing machinesrequire the substrate to be in tension as the substrate is fed throughvarious rolls, rollers and drums. As the polymer heats up, its yieldstrength may begin to lower. If the polymer increases in temperature toomuch, the polymer may begin to deform as it passes through theroll-to-roll machine. This can lead to buckles, jams, and/or unevendeposition onto the substrate.

It may be that the temperature of the substrate does not exceed 500degrees Celsius at any point during the plasma deposition process, andoptionally does not exceed 200 degrees Celsius.

It may be that the step of using the sputter deposition technique todeposit material onto the substrate is performed at temperatures suchthat the maximum temperature reached at any given time by any givensquare of substrate material having an area of 1 cm² as measured on thesurface opposite to said surface on which the material is deposited andas averaged over a period of 1 second, may be no more than 500° C.,optionally no more than 300° C., optionally no more than 200° C.,optionally no more than 150° C., optionally no more than 120° C. andoptionally no more than 100° C.

The method may also optionally comprise the sputtering of material undera reactive sputtering regime, using oxygen as a reactive gas.

In a reactive sputtering method, a reactive gas is introduced into theprocess, along with an inert sputter gas. The inert sputter gas may beargon. This allows elemental targets to be used, and oxides to form aspart of the plasma sputtering process. Generally, the structure and formof the oxide produced may be adjusted, by providing the reactive oxygengas at a higher or lower flow rate.

The ratio of the power used to generate the plasma to the powerassociated with the bias on the target may be greater than or equal to1:1, optionally less than or equal to 7:2 and is optionally less than orequal to 3:2. The applicant has discovered that such power ratios may bebeneficial in depositing crystalline materials without the need toanneal the material so deposited.

The actual power in the plasma may be less than the power used togenerate the plasma. In this connection, the efficiency of thegeneration of the plasma ([actual power in the plasma/power used togenerate the plasma]×100) may typically be from 50% to 85%, typicallyabout 50%.

The remotely generated plasma may be of high energy.

The remotely generated plasma may be of high density. In thisconnection, the plasma may have an ion density of at least 10¹¹ cm⁻³.

The power density associated with the voltage bias of the target isoptionally greater than 1 Wcm⁻² and optionally up to 100Wcm².

The surface onto which the material is deposited may have a surfaceroughness X_(S) or less, where X_(S)=100 nm, and the deposited materialmay form a layer that may have a thickness of from 0.01 to 10 μm and asurface roughness of no more than X₁, where X₁ equals the product of Fand X_(S), where F is a factor in the range of 1 to 2.

X_(S) may be no more than 10% of the thickness of the substrate. Theproduct of the thickness of the substrate and X_(S) may be no more than10⁵ nm².

The substrate, optionally a polymer substrate, may be provided withembedded particles and of all of the embedded particles within or on thepolymer material, the majority of those that contribute to surfaceroughness of the substrate have a median size from 10% to 125% of X_(S).

Alternatively, the substrate, optionally a polymer substrate, may beprovided with embedded particles and of all of the embedded particleswithin or on the polymer material, the majority of those that contributeto surface roughness of the substrate have a median size of no less than150% of X_(S).

The method may include a step of depositing material onto the surfaceusing sputter deposition to form a further layer having a thickness offrom 0.01 to 10 μm and a surface roughness of no more than 150% ofX_(S), the material composition of the crystalline layer being differentfrom the material composition of the further layer.

It may be that electron density distribution of the plasma is relativelyuniform for different cross-sections taken across it volume. The plasmamay be constrained or confined using magnets and/or electrostatics tohave a certain overall shape that has a width and/or length much greaterthan its thickness. The width and length of the plasma cloud may each beat least five times greater than the thickness. The plasma may have awidth which is aligned with the width of the substrate. There may be apair of antennae on opposing sides of plasma separated by distance L(the lengthwise direction of the plasma) each having length, W (thewidth-wise direction of the plasma). The thickness of plasma may bedefined either by the maximum extent of the glow in visible spectrum orthe largest distance as measured in the direction perpendicular to bothL and W which covers 90% of the free electrons in the plasma.

The generating of plasma may be performed by at least one antennaextending in a direction parallel to the width of the substrate. Thereare preferably a pair of such antennae. Preferably the, or each, antennaextends across the majority of the width of, possibly at leastsubstantially the entire width of, the substrate.

Magnetic and/or electrostatic fields may be used to confine the plasma,for example so as to be proximate the target and to extend and propagatewithin the substantially common plane of the target and the substrate.

The magnetic and/or electrostatic fields may confine the plasma bypropagating the plasma in a direction transverse to the width of thesubstrate.

The method preferably comprises confining the plasma using magneticand/or electrostatic fields so that the electron density distribution ofthe plasma forms a blanket and/or a sheet (e.g. a plasma cloud soconfined that, although not necessarily planar in shape, has a thicknessthat does not vary significantly along at least one of the width and thelength of the plasma cloud). The plasma may be confined to form a sheetand/or blanket that extends in a direction along the width of thesubstrate and in a direction along the length of the substrate.

The working distance between at least one target of the first targetassembly and the substrate may be within +/−50% of the theoretical meanfree path of the system.

Without wishing to be bound by theory, it is believed that the workingdistance has an influence on the “ad atom” energy of the sputteredmaterial as it deposits onto the substrate. In a case where the workingdistance is greater than the mean free path of the system, it is thoughtthat it is more likely that an ion in the sputter flux would be involvedin a collision before reaching the substrate, resulting in relativelylow ad atom energy. Conversely, if the working distance is shorter thanthe mean free path of the system, the ad atom energy is relatively high.Differences in the separations of the respective targets of the firstand second target assemblies from the substrate may be used as anadditional control over the stoichiometry of the material deposited.

A definition of the mean free path is the average distance betweencollisions for an ion in the plasma. The mean free path is calculatedbased on the volume of interaction (varied by the working distance), andthe number of molecules per unit volume (varied by the workingpressure).

The working distance is optionally at least 3.0 cm, optionally at least4.0 cm and optionally 5.0 cm. The working distance is optionally no morethan 20 cm, optionally no more than 15 cm and optionally no more than 13cm. The working distance may be from 4.0 cm to 13 cm, optionally from6.0 cm to 10 cm, and optionally from 8.0 cm to 9.0 cm. It may be thatthe working distance between at least one target of the first targetassembly and the substrate is from 5 cm to 20 cm.

The working pressure may be from 0.00065 mBar to 0.010 mBar, optionallyfrom 0.001 to 0.007mBar. A higher working pressure in this range mayresult in a higher deposition rate. This is because a higher workingpressure results in a larger number of process ion (usually Ar+)bombardments on the surface of the target, and hence material issputtered from the target at a higher rate.

When the working distance is from 8.0 to 9.0 cm, the range ofcrystallite sizes available may be narrower, for example, if a workingpressure of from 0.0010 mBar to 0.0065 mBar is used. The crystallitesize may be from 14 to 25 nm. This is evidence that within theseparameter ranges, it is possible to form films with narrow andpredictable thin film ranges.

The working distance between at least one target of the second targetassembly and the substrate may be within +/−50% of the theoretical meanfree path of the system.

The working distance between at least one target of the first targetassembly and the substrate may be within +/−50% of the working distancebetween at least one target of the second target assembly and thesubstrate.

It may be that the crystalline layer formed on the surface has athickness of from 0.001 to 10 μm, optionally a thickness of from 0.5 to10 μm. The thickness of the deposited material on completion of themethod is optionally no more than 1.0 micron.

The substrate may have a thickness of up to 10 μm. For example, thesubstrate may have a thickness of from 0.1 to 10 μm. The thickness ofthe substrate is optionally no more than 1.6 microns. The thickness ofthe substrate provided is optionally less than 1.0 microns. 0.9 microns.

It is beneficial when designing solid state batteries for the substrateto be as thin as possible (if the substrate is to form part of the endproduct). This allows for batteries with a higher energy density to bemanufactured. Preferably, if a thinner substrate became available, whichmet the preferable requirements of a relatively high temperaturecorrected yield strength and/or high degradation point, such a substratewould be used for the method.

It may be that the substrate is retained as a part of the end-useelectronic product or component.

It may be that the substrate is a sacrificial substrate. It may be thatthe substrate is removed before the layer(s) of material. Part or all ofthe substrate may be removed before integrating the crystalline layer ora part thereof in an electronic product package, component or other endproduct. For example, the layer of crystalline material may be liftedoff from the substrate. There may be a layer of other interveningmaterial between the base substrate and the crystalline material. Thislayer may lift off with the crystalline material or assist in theseparation of the crystalline material from the base substrate. Alaser-based lift-off technique may be used. The substrate may be removedby a process that utilises laser ablation.

Similar techniques are described in the prior art. For example,KR20130029488 describes a method of making a battery including using asacrificial substrate and laser radiation to harvest a battery layer.

According to a further aspect of the invention, there is provided amethod of manufacturing an electronic component including forming amultilayer sheet of different materials, integrating the multilayersheet or a part thereof in an electronic product. At least one of thelayers of the sheet is preferably a crystalline layer of conducting orsemiconducting material made by performing the method of the inventionas described or claimed herein. The electronic component may be abattery, a functional layer of a battery, an energy storage device or acell of battery.

According to a yet further aspect of the invention, there is provided abattery comprising one or more layers of crystalline material formed byperforming the method of the invention as described or claimed herein.Such a battery may comprise multiple stacked cathode layers, multiplestacked electrolyte layers, and multiple stacked anode layers. It may bethat at least two of the multiple stacked cathode layers are made byperforming the method of the invention as described or claimed herein.

It will of course be appreciated that features described in relation toone aspect of the present invention may be incorporated into otheraspects of the present invention. For example, the method of theinvention may incorporate any of the features described with referenceto the apparatus of the invention and vice versa.

DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying schematic drawings whichcan be briefly summarised as follows.

FIG. 1 a is a schematic side-on view of a plasma deposition chamber usedin accordance with a first example;

FIG. 1 b shows the steps of a method of manufacturing a battery cathodein accordance with the first example;

FIGS. 1 c to 1 h are schematic illustrations of various polymersubstrate materials in cross-section;

FIG. 2 a is a schematic side-on view of a plasma deposition chamber usedin accordance with a second example method;

FIG. 2 b is an X-ray diffraction (XRD) spectra of a first sample of abattery cathode made in accordance with the method of the secondexample;

FIG. 2 c is a Raman spectra of a battery cathode from which the XRD dataof FIG. 2 b are obtained;

FIG. 2 d is an XRD spectra of a second sample of a battery cathode madein accordance with a method of the second example;

FIG. 2 e is a Raman spectra of the battery cathode from which the XRDdata of FIG. 2 d are obtained;

FIG. 3 a is a schematic side view of a plasma deposition chamber used ina method in accordance with a third example;

FIG. 3 b is a schematic plan view of the plasma deposition chamber shownin FIG. 3 a;

FIG. 3 c is a further schematic side view of the plasma depositionchamber shown in FIGS. 3 a and 3 b;

FIG. 3 d is a graph comparing sputter yields of cobalt and lithium as afunction of energy;

FIG. 3 e is a schematic side view of a plasma deposition chamber used ina method in accordance with a fourth example;

FIG. 4 a is a cross-sectional scanning electron micrograph of a batterycathode relating to a first sample made using in accordance with themethod of the second example;

FIG. 4 b is a birds-eye view of a scanning electron micrograph of abattery cathode relating to a second sample made in accordance with themethod of the second example;

FIG. 5 a is a schematic cross-section through a battery cathode relatingto a first sample made using a method of a fifth example;

FIG. 5 b is a schematic cross-section through a battery cathode relatingto a second sample made using the method of the fifth example;

FIG. 5 c shows the steps of a method of manufacturing a battery cathodichalf-cell in accordance with the fifth example;

FIG. 6 is a schematic representation of an example of a method of makinga battery cell in accordance with a sixth example;

FIG. 7 a is a schematic representation of an example of a method ofmanufacturing a solid-state thin film battery in accordance with aseventh example;

FIG. 7 b is a schematic cross-section through a solid-state thin filmbattery in accordance with a first sample of the seventh example;

FIG. 7 c is a schematic cross-section through a sample solid state thinfilm battery made in accordance with a second sample of the seventhexample;

FIG. 8 a is a schematic representation of a method of determining anoptimum working distance for a remote plasma deposition systemconfigured for the deposition of layered oxide materials in accordancewith an eighth example;

FIG. 8 b shows a number of X-Ray diffraction spectra collected as partof the method of FIG. 8 a , where the characterisation technique isX-Ray diffraction and the characteristic feature is a characteristicX-Ray diffraction peak associated with a layered oxide structure;

FIG. 9 a is a micrograph of a sample film formed in accordance with thefirst example of the invention;

FIG. 9 b is an X-ray diffraction spectra obtained from the film shown inFIG. 9 a;

FIG. 10 a a schematic representation of an example of a method ofdetermining an optimum working pressure for a remote plasma depositionsystem configured for the deposition of layered oxide materials inaccordance with a ninth example;

FIG. 10 b shows two X-Ray diffraction spectra collected as part of themethod as described with reference to FIG. 10 a , where thecharacterisation technique is X-Ray diffraction and the characteristicfeature is a characteristic X-Ray diffraction peak associated with alayered oxide structure;

FIG. 11 a is an example of the steps of a method of determining thecrystallite size of layered oxide materials in accordance with a tenthexample;

FIG. 11 b is a graph showing how to determine the crystallite size atdifferent working pressures in accordance with the tenth example, for aworking distance of 16 cm, showing the crystallite size for a number offilms deposited in accordance with the first example;

FIG. 11 c is a graph showing how to determine the crystallite size atdifferent working pressures in accordance with the tenth example, for aworking distance of 8.5 cm, the crystallite size for a number of filmsdeposited in accordance with the first example;

FIG. 12 is a schematic representation of a method of depositing amaterial on a substrate in accordance with an eleventh example of theinvention;

FIG. 13 is a schematic representation of an example of a method ofmanufacturing a component for an electronic device in accordance with atwelfth example;

FIG. 14 is a schematic representation of an example of a method ofmanufacturing a component for an electronic device, in accordance withthe thirteenth example of the invention;

FIG. 15 is a schematic representation of an example of a method ofmanufacturing a Light Emitting Diode (LED) in accordance with afourteenth example of the invention;

FIG. 16 is a schematic representation of an example of a method ofmanufacturing a permanent magnet in accordance with a fifteenth exampleof the invention; and

FIG. 17 is a schematic representation of an example of a method ofmanufacturing an electronic device comprising a layer of Indium TinOxide (ITO) in accordance with a sixteenth example of the invention.

DETAILED DESCRIPTION

FIG. 1 a is a schematic side-on view of a plasma deposition processapparatus which is used in a method of depositing a (crystalline)material onto a substrate in accordance with a first example. The methodis denoted generally by reference numeral 1001 and is shownschematically in FIG. 1 b , and comprises generating 1002 a plasmaremote from one or more targets, exposing 1003 the plasma target ortargets to the plasma such that target material is sputtered from one ormore targets, and exposing 1004 a first portion of a substrate tosputtered material such that the sputtered material is deposited ontothe first portion of the substrate, thereby forming crystalline materialonto the first portion of the substrate. The method of depositing a(crystalline) material onto the substrate may be performed as a part ofa method of manufacturing a battery cathode.

The crystalline material in this example takes the form ABO₂. In thepresent example, the ABO₂ material takes a layered oxide structure. Inthe present example, the ABO₂ material is LiCoO₂. However, the method ofthe present example has been shown to work on a wide range of ABO₂materials. In other examples, the ABO₂ material structure comprises atleast one of the following compounds (described here with non-specificstoichiometry): LiCoO, LiCoAlO, LiNiCoAlO, LiMnO, LiNiMnO, LiNiMnCoO,LiNiO and LiNiCoO. These materials are potential candidates formanufacturing a battery cathode. Those skilled in the art will realisethat the stoichiometry may be varied.

In this example, the ABO₂ material is LiCoO₂ and is deposited as a layerthat is approximately 1 micron thick. In other examples, the ABO₂material is deposited as layer that is approximately 5 microns thick. Inyet further examples, the ABO₂ material is deposited as a layer that isapproximately 10 microns thick.

With reference to FIG. 1 a , the plasma deposition process apparatus isdenoted generally by reference numeral 100 and comprises a plasma targetassembly 102 comprising a target 104, a remote plasma generator 106, aseries of electromagnets 108 for confining the plasma generated by theremote plasma generator 106, a target power supply 110, a remote plasmasource power supply 112 and a housing 114. Remote plasma generator 106comprises two pairs of radio frequency (RF) antennae 116. Housing 114comprises a vacuum outlet 120 which is connected to a series of vacuumpumps located outside the chamber so that the chamber 122 defined byhousing 114 can be evacuated. Housing 114 is also provided with a gasinlet 124 which may be connected to a gas supply (not shown) for theintroduction of one or more gases into the chamber 122. In otherexamples, the gas inlet 124 may be positioned over the surface of thetarget assembly 102. As can be seen from FIG. 1 a , the plasma isgenerated remote from the target 104.

In this example, the target 104 comprises material LiCoO₂. Briefly, thechamber 122 is evacuated until a sufficiently low pressure is reached.Power provided by power supply 112 is used to power the remote plasmagenerator 106 to generate a plasma. Power is applied to the target 104such that plasma interacts with target 104, causing LiCoO₂ to besputtered from the target 104 and onto the substrate 128. In the presentexample, the substrate 128 comprises a polymer sheet which is introducedinto the housing 114 via inlet 130 and out of the housing 114 via outlet132. A powered roller 134 is used to help move the substrate 128. TheLiCoO₂ is deposited onto the substrate 128 as a crystalline(non-amorphous) material.

The apparatus 100 also comprises a shutter 136, for restrictingdeposition of sputtered material onto the substrate 128, and an input138 for cooling the drum. Shutter 136 allows a portion of the substrate128 to be exposed to the sputtered material.

As mentioned above, a powered roller 134 is used to help move thesubstrate 128 into and out of the plasma deposition apparatus 100.Powered roller 134 is part of a roll-to-roll substrate handlingapparatus (not shown) which comprises at least a first storage rollerupstream of the plasma deposition apparatus 100 and a second storageroller downstream of the plasma deposition apparatus 100. Theroll-to-roll substrate handling apparatus is a convenient way ofhandling, storing and moving thin, flexible substrates such as thepolymer substrate used in this example. Such a roll-to-roll system has anumber of other advantages. It allows for a high material throughput andallows a large cathode area to be deposited on one substrate, throughouta series of depositions at a first portion of the substrate, followed bya second portion of the substrate, and so on. Furthermore, suchroll-to-roll processing allows for a number of depositions to occurwithout breaking vacuum. This saves both time and energy compared tosystems in which the chamber needs to be taken back up to atmosphericpressure from vacuum after deposition in order to load a new substrate.In other examples, sheet-to-sheet processing is used instead ofroll-to-roll processing, wherein the substrate is provided with asupport. Alternatively, the substrate may be supplied in discrete sheetsthat are handled and stored in relatively flat sheets. The substrate maybe planar in shape as the material is deposited thereon. This may be thecase, when the substrate is provided in the form of discrete sheets, notbeing transferred to or from a roll. The sheets may each be mounted on acarrier, having greater structural rigidity. This may allow for thinnersubstrates to be used than in the case of substrate film held on aroller. It may be that the substrate is a sacrificial substrate. It maybe that the substrate is removed before the layer(s) of material. Partor all of the substrate may be removed before integrating thecrystalline layer or a part thereof in an electronic product package,component or other end product. For example, the layer of crystallinematerial may be lifted off from the substrate. There may be a layer ofother intervening material between the base substrate and thecrystalline material. This layer may lift off with the crystallinematerial or assist in the separation of the crystalline material fromthe base substrate. A laser-based lift-off technique may be used. Thesubstrate may be removed by a process that utilises laser ablation.

Similar techniques are described in the prior art. For example,KR20130029488 describes a method of making a battery including using asacrificial substrate and laser radiation to harvest a battery layer. Inother examples, another suitable processing regime is used, provided itis capable of sufficiently high production throughput.

The polymer substrate 128 is under tension when moving through thesystem, for example withstanding a tension of at least 0.001N during atleast part of the processing. The polymer is robust enough such thatwhen the polymer is fed through the roll-to-roll machine, it does notexperience deformation under tensile stress. In this example, thepolymer is Polyethylene terephthalate (PET), and the substrate 128 has athickness of 1 micron or less, in examples the thickness is 0.9 microns.The substrate 128 is pre-coated with a current collecting layer, whichis made of an inert metal. In this example, the inert metal used as thecurrent collecting layer is platinum. The yield strength of the PET filmis sufficiently strong that the substrate does not yield or plasticallydeform under the stresses of the roll-to-roll handling apparatus. Theinert metal used in other examples can alternatively be gold, iridium,copper, aluminium or nickel.

The use of such thin polymer substrates is beneficial because thisfacilitates batteries with a higher energy density to be manufactured.In other examples, a material, which is not polymeric, is used,providing that it can be manufactured in a sufficiently thin andflexible manner to allow for a high battery density and ease of handlingpost-deposition.

The plasma deposition process and subsequent manufacturing processes arehowever subject to the technical challenges that working with such thinlayers impose.

Before the substrate 128 is so pre-coated, it has a surface roughnessthat is carefully engineered so as (a) to be great enough to mitigatethe undesirable effects that would otherwise result from electrostaticforces (such as increasing the force required to unwind the polymer filmfrom the drum on which it is held) and (b) to be small enough that theroughness does not cause problems when depositing material onto thesubstrate. In this example, the surface roughness is engineered to beabout 50 nm. It will be noted that the product of the thickness of thesubstrate (0.9 microns) and the surface roughness is 4.5×10⁴ nm² and istherefore less than 10⁵ nm² and less than 5×10⁴ nm² in this example. Ithas been found that that the roughness needed for easing handling ofthin films rises with decreasing thickness. Generally, it has been foundthat the roughness required to improve handling of thinner substrates(i.e. less than 10 microns, particularly less than 1 micron) increasesas the substrate thickness decreases.

FIG. 1 c shows (not to scale) a typical thin-film polymer being about 1micron thick and having embedded particles providing roughness. Theroughness of the surface features provided by the particles is at least90 nm and possibly higher. This is too rough for the particular exampleenvisaged (although may be acceptable for other examples).

FIG. 1 d shows (not to scale) one way in which the desired roughness canbe achieved. Spherical particles of polystyrene are embedded in thesubstrate material such that at least 90% of those which contribute tothe roughness of the substrate protrude from the local substrate surfaceby no more than half the volume of the particle. The particles have adiameter of about 90 nm. Thus, a majority of the embedded particles thatcontribute to surface roughness of the substrate have a median size ofabout 180% of the surface roughness of the substrate. In other examples,the embedded spherical particles are made of different material, such assilicon oxide.

FIG. 1 e shows (not to scale) an alternative way in which a desiredroughness can be achieved. Spherical embedded particles of polystyreneare present on the surface of the substrate material such that at least90% of those which contribute to the roughness of the substrate protrudefrom the local substrate surface by more than half the volume of theparticle. The particles used in the example of FIG. 1 e are smaller thanthose used in the example of FIG. 1 d.

Examples such as those of FIGS. 1 d and 1 e enable good quality films tobe deposited, as crystalline material, on thin substrates in amanufacturing environment. The advantages of the presence of embeddedparticles are retained, but by careful control of the location and sizedistribution of such particles, the potential disadvantages can beavoided or reduced. FIGS. 1 f to 1 h show schematically a cross-sectioncorresponding to the substrate shown in FIGS. 1 c to 1 e after a layerof crystalline material has been formed on the substrate surface. Theintermediate layer of metal current collector is omitted from FIGS. 1 fto 1 h . The roughness of the substrate shown in FIGS. 1 c and 1 f issuch that problems arise. The dominating protrusions caused by certainembedded particles 152 cause shadowing and competing crystal growth,which are illustrated schematically by means of the contrasting shading154 in FIG. 1 f . This competing crystal growth which is aligned in aconflicting direction gives rise to discontinuities in the layer thataffects performance of the final product. Also, there is a surprisinglyprofound effect on the likelihood of delamination of the layer ofdeposited material from the substrate. This may be as a result of poorcontact between the deposited layer and the underlying substrate in theregion near to any embedded particles that protrude far from the medianplane of the surface (illustrated schematically by the voids 156 in FIG.1 f ), where the local asperity radius is small In contrast, it can beseen from FIGS. 1 g and 1 h that no such problems arise. The roughnessof the surface of the material deposited on the substrate isapproximately 50 nm.

The roughness of the substrate can be measured with a profilometer. Thisinstrument has a stationary stylus. The surface to be measured istranslated under the stylus, and the deflections of the stylus measurethe surface profile, from which various roughness parameters arecalculated.

Roughness can also be measured using “non-contact” methods. A suitablemachine for measuring roughness is the “Omniscan MicroXAM 5000B 3d”which uses optical phase shift interference to measure the surfaceprofile.

The roughness, Ra, can be calculated using the formula

$R_{a} = {\frac{1}{n}{\sum\limits_{i = 1}^{n}{❘y_{i}❘}}}$

where the deviation y from a smooth surface is measured for n datapoints.

The surface roughness, Sa, of an area A extending in the x- andy-directions can be calculated using the formula:

$s_{a} = {\frac{1}{A}{\int{\int_{A}{{❘{Z\left( {x,y} \right)}❘}{dxdy}}}}}$

where Z is the deviation from a mathematically perfectly smooth surface.

In the present example, the average surface roughness is measured with anon-contact method.

The remotely generated plasma is created by the power supplied to theantennae 116 by power supply 112. There is therefore a measurable powerassociated with that used to generate the plasma. The plasma isaccelerated to the target by means of electrically biasing the target104, there being an associated electrical current as a result. There isthus a power associated with the bias on the target 104. In thisexample, the ratio of the power used to generate the plasma to the powerassociated with the bias on the target is greater than 1:1, andoptionally greater than 1.0:1.0. Note that in this example, the ratio iscalculated on the assumption that the power efficiency of theplasma-generating source is taken to be 50%. The power associated withthe bias on the target is at least 1 Wcm⁻².

In further examples, the ratio of the power used to generate the plasmato the power associated with the bias on the target is greater than 1:1,and no more than 7:2, optionally 7.0:2.0. In yet further examples, thepower associated with the bias on the target is greater than 1:1 and nomore than 3:2, optionally 3.0:2.0. In some examples, the powerefficiency of the plasma generating source is taken to be 80%. In someexamples, the power associated with the bias on the target is 10 Wcm⁻².In yet further examples, the power associated with the bias on thetarget is 100 Wcm⁻². In yet further examples, the power associated withthe bias on the target is 800 Wcm⁻². In other examples, the efficiencyof the plasma generating source may be different, and the power ratiomay also be different.

When the LiCoO₂ film is deposited onto the substrate, it forms acrystalline film of LiCoO₂. The crystalline structure which forms ontothe substrate is in the R3m space group. This structure is a layeredoxide structure. This structure has a number of benefits, such as havinga high accessible capacity and high rate of charge and dischargecompared to the low energy structure of LiCoO₂, which has a structure inthe Fd3m space group. Crystalline LiCoO₂ in the R3m space group is oftenfavoured for solid state battery applications.

Throughout the plasma deposition process, the temperature of thesubstrate 128 does not exceed the degradation point of the polymersubstrate 128. Moreover, the temperature of the substrate issufficiently low throughout the deposition process such that thetemperature adjusted yield stress of the polymer substrate remainssufficiently high such that the polymer substrate does not deform underthe stresses exerted by the roll-to-roll processing machine.

The general shape of the confined plasma made from the remote plasmagenerator 106 is shown by the dashed lines B in FIG. 1 a . The series ofelectromagnets 108 is used to and confine the plasma to a desiredshape/volume.

It should be noted that, whilst in this first example, substrate 128 isfed into the chamber at inlet 130, and exits the chamber at outlet 132,alternative arrangements are possible. For example, the roll or otherstore upstream of shutter 136 may be inside the process chamber 122. Theroll or other store downstream of shutter 136 may be inside or could bestored inside the process chamber 122.

In addition the means 112 of powering the plasma source, may be of RF,(Direct Current) DC, or pulsed-DC type.

In this first example, the target assembly 102 comprises only one target104. This target is made of LiCoO₂. It should be appreciated thatalternative and/or multiple target assemblies may be used, for example,comprising a distinct region of elemental lithium, a distinct region ofelemental cobalt, a distinct region of lithium oxide, a distinct regionof cobalt oxide, a distinct region of a LiCo alloy, a distinct region ofLiCoO₂, or any combination thereof. In other examples, the ABO₂ materialmay not be LiCoO₂. In these examples, the target assembly or assembliescontain distinct regions of A, distinct regions of B, distinct regionsof a compound containing A and/or B, and/or distinct regions containingABO₂.

For the avoidance of doubt, the target 104 of the target assembly 103acts as a source of material alone and does not function as a cathodewhen power is applied to it from the RF, DC or pulsed DC power supply.

In this example, the working pressure of the system is 0.0050 mBar. Thetheoretical mean free path of the system is approximately 10 cm. Thetheoretical mean free path is the average distance between collisionsfor an ion in the plasma. The working distance between the target 104and substrate 128 is approximately 8.5 cm. This working distance istherefore approximately 85% of the theoretical mean free path of thesystem.

In this example, the working pressure is above a lower bound below whichcrystalline material in the layered oxide structure does not form, butbelow an upper bound above which observable damage is caused to thesubstrate. The working distance is shorter than an upper bound abovewhich crystalline material in the layered oxide structure does not form,and longer than a lower bound below which the energy of the depositioncauses observable damage to the substrate, or unfavourable oxide statesto form.

The average crystallite size of the crystallites which form on the filmin this example is around 20 nm. In other examples, the averagecrystallite size of the crystallites which form on the film is around 50nm.

In an alternative example, the working pressure of the system is 0.0020mBar. The theoretical mean free path of the system is approximately 12cm. The working distance between the target 104 and substrate 128 isapproximately 9 cm. This working distance is therefore approximately 75%of the theoretical mean free path of the system.

In an alternative example, the working pressure of the system is 0.0065mBar. The theoretical mean free path of the system is approximately 15cm. The working distance between the target 104 and substrate 128 isapproximately 7.5 cm. This working distance is therefore approximately50% of the theoretical mean free path of the system.

A second example method uses the apparatus shown in FIG. 2 a . The maindifferences between the apparatus of FIG. 1 a and the apparatus of FIG.2 a will now be described. FIG. 2 a shows that instead of the flexiblesubstrate 128 presented in the first example, an inflexible planar glasssubstrate 228 is used. Furthermore, no shutter is present in thisexample. The thickness of the glass substrate is in the order ofmillimetres. A single target 204 is used in this example. A thermalindicator sticker was attached to the face of the glass slide oppositeto that on which the cathode material was deposited. The thermalindicator sticker is configured to indicate whether or not the substrate228 experienced a temperature of 270° C. or more during the plasmadeposition process. After deposition, the sticker indicated that thesubstrate did not experience a temperature of 270° C. or more during thedeposition process. The general shape of the plasma is indicated by thearea enclosed by the broken line B′ in FIG. 2 a.

Table 1 shows the properties of the resultant exemplary battery cathodesproduced in accordance with the second example:

TABLE 1 properties of LiCoO₂ cathode films as a function of depositionparameters Plasma Ar Measured film source Process process Film Film DepExample Target Composition (At %) power Sputtering pressure flow ratethickness Roughness time identifier composition O Co Li (W) Power (W)(mBar) (SCCM) (nm) Sa (nm) (min) Sample 1 LiCoO₂ 56 21 23 1800 5003.90e−03 52 910 51.8 100 Sample 2 LiCoO₂ 55 21 24 1800 800 3.90e−03 52915 106 100

In Table 1 above, the elemental film composition was determined by x-rayphotoelectron spectroscopy using a Themo Fisher K-alpha spectrometerwith a MAGCIS ion gun. Quoted compositions were taken from depthprofiling measuring at about 10 levels with a film. Plasma source poweris the electrical power supplied to generate the plasma. Sputteringpower is the electrical power applied to the target 204. Processpressure is the pressure in the chamber. Film thickness and roughnessmeasurements were taken after deposition, using an Omniscan MicroXAM5000b 3d optical profiler. Film thicknesses were measured afterdeposition, as step-heights at masked edges and roughness measurementswere taken from sample areas of about 400 microns×500 microns.

FIG. 2 b shows an X-ray diffraction (XRD) spectra of the battery cathodeof Sample 1. The structure of the film was characterised by X-raydiffraction using a diffractometer (Rigaku-Smartlab) with nickelfiltered CuKα radiation (λ=1.5406 Å). The diffraction pattern was takenat room temperature in the range 10°<2 θ<80° using a fixed incidentangle of <5°. Data were collected using step scans with a resolution of0.04°/step and a count time of 0.5s/step. The peak at approximately 37°is associated with the (101) plane of the crystals being substantiallyorientated parallel to the substrate surface. The peak at approximately66° is associated with the crystals being substantially oriented suchthat the (110) plane is parallel to the substrate. The peak atapproximately 55° is associated with the glass substrate, and for thepurposes of determining the crystal structure of the LiCoO₂, should beignored.

The absence of extra reflections associated with the Fd3m space group isan initial indicator that the LiCoO₂ deposited is in the R3m spacegroup.

Also notably absent is the peak associated with the (003) plane. Thisimplies that very few crystals are orientated in such a way that the(003) plane is parallel to the substrate surface. It is beneficial thatvery few crystals are orientated in this way. A detailed explanation isbeyond the scope of the present application, but briefly, the accessiblecapacity of a cathode increases when a higher proportion of the crystalsare aligned such that the (101) and (110) planes are parallel to thesubstrate, as opposed to being aligned such that the (003) plane isparallel to the substrate as the apparent resistance to ion migration islower. The crystals have formed such that the longitudinal axis of thecrystals is normal to the substrate. In other words, the crystals haveformed in an epitaxial manner.

The applicant has discovered that if the ratio of the power used togenerate the plasma to the power associated with the biasing of thetarget is more than 1:1, then generally a crystalline material isdeposited. In Sample 1, the ratio is 1800:500 (3.6:1) and in Sample 2,the ratio is 1800:800 (9:4). Note that in this example, the ratio iscalculated on the assumption that the power efficiency of theplasma-generating source is taken to be 50%.

In a comparative example, the experiment was repeated with a plasmasource power of 1 kW and a power associated with bias to the target of 1kW. The material deposited was substantially amorphous. The performanceof the film of the comparative example as a cathode was investigated bydepositing an electrolyte (in this case, LiPON) and an anode metal ontop of the cathode layer, thereby making a solid state battery. Thecharge-discharge characteristics of the battery were investigated andwere found to be poor, with a cathode specific capacity of about 10mAh/g. When analogous batteries were made using crystalline LiCoO₂ suchas that formed in Sample 1 and Sample 2, the charge-dischargecharacteristics were far superior, with typical cathode specificcapacities of about 120 mAh/g.

FIG. 2 c shows a Raman spectra of the battery cathode of Sample 1. Thebonding environment of the films was characterised by Raman Spectrocopy.Raman spectra were collected using a JY Horiba LabRAM ARAMIS imagingconfocal Raman microscope using 532 nm excitation. Note that the strongsharp peak at 600 cm⁻¹ can be considered as anomalous due to theunphysical nature of the sharpness of the peak. The strong,characteristic peak observed at 487 cm⁻¹ is well known in the art to beassociated with the R3m space group crystal structure of LiCoO₂.

FIG. 2 d shows an XRD spectra (collected in the same way as that forSample 1) of the cathode of Sample 2. The spectra shown is similar tothat shown in FIG. 2 b . However, in FIG. 2 d , the relative intensityof the peak at approximately 66° is far stronger than that of the peakat 37°. This indicates that the number of crystals with their (110)planes parallel to the substrate is higher than the number of crystalswith their (101) planes parallel to the substrate for Sample 2. This isbeneficial as it means that the ion channels of the thin film areorientated perpendicular to the substrate, making for easier forintercalation and de-intercalation of the ions from their interstitialsites from within the crystal structure of the cathode. This improvesthe accessible capacity and the rate of charge of the cathode. FIG. 2 eis a Raman spectra of the cathode of Sample 2; the same comments applyto FIG. 2 e that apply to FIG. 2 c.

FIGS. 3 a to 3 c show an alternative example of an apparatus for use inanother example of a method of manufacturing a layer of crystallinematerial on a surface using plasma sputtering according to a thirdexample. The apparatus and method of manufacture employed is similar tothat described with reference to the first example. Only the significantdifferences will now be described. The same parts are labelled withreference numerals sharing the same last two digits. For example,rotating drum 334 in FIG. 3 a is the same as rotating drum 134 in FIG. 1a . The apparatus of FIG. 3 a comprises a rotating drum 334 on which apolymer substrate 328 is supported within a region defined by a processchamber 322 (the walls of the chamber being omitted for the sake ofclarity). The target assembly 302 comprises a plurality of targets.There is provided a first target 304 consisting of elemental lithium anda plurality of targets 303 consisting of elemental cobalt (referred tonow as the second targets). The targets are all positioned at a workingdistance of about 10 cm from the substrate 328 (the working distancebeing shortest separation therebetween). The surface of each target 303,304 facing the drum 334 is flat (and planar). The radius of the drum 334is significantly greater than the working distance (the size of the drum334 being shown in the Figures as being relatively smaller than it is inreality for the sake of the illustration). The targets 303, 304 arearranged circumferentially around the circumference of the drum 334. Theapparatus also comprises a shutter 336, for restricting deposition ofsputtered material onto the substrate 328.

A plasma of argon ions and electrons is generated by means of twoelectrically powered spaced apart antennae 316. The plasma is confinedand focussed by a magnetic field controlled by two pairs ofelectromagnets 308, each pair being positioned proximate to one of theantennae 316 and the electric field generated by the system. The overallshape of the plasma (the 90% highest concentration of which beingillustrated in highly schematic fashion in FIG. 3 c by the plasma cloudB″) is that of a blanket, in that the length and width of the plasmacloud are much greater than the thickness. The width of the plasma iscontrolled in part by the length of the antennae 316. The two pairs ofantennae 316 are separated by a distance that is comparable to thelength of the plasma. The length and width of the plasma are in the samegeneral direction as the length and width, respectively, of thesubstrate.

The plasma source is spaced apart from the targets, and may thus beconsidered as a remotely generated plasma. The theoretical mean freepath of the system (that is, the average distance between collisions foran ion in the plasma) is about 12 cm, meaning that the majority ofparticles travel from the target to the substrate without colliding withany argon ions in the plasma.

FIG. 3 a is a partial schematic cross-sectional view showing part of thesubstrate travelling on the drum 334 and also shows schematically thetrajectories of particles that travel from the targets 303, 304 to thesubstrate. Thus, there is a first plume corresponding to thetrajectories of particles from the first target 304 to the surface ofthe substrate 328 and a second plume corresponding to the trajectoriesof particles from the second target 303 to the surface of the substrate328. The first plume is shown as a spotted region and each second plumeis shown as a solid grey region. It will be seen from FIG. 3 a that thefirst plume and the second plume converge at a region proximate to thesubstrate. It will also be seen in FIG. 3 a that the first target 304faces towards the substrate in a first direction (defined in thisexample by the notional line extending from the centre of the surface ofthe target 304) and the adjacent second target 303 to the left as shownin FIG. 3 a , faces towards the substrate in a second direction (definedin this example by the notional line extending from the centre of thesurface of the target 303). The first and second directions convergetowards the substrate and intersect at a location just beyond thesubstrate (the location being about 3 cm beyond the substrate). Oxygengas is supplied at a controlled rate into the process chamber 322through inlets 325. The targets are stationary as the substrate moveswith rotation of the drum. In other examples, the inert sputtering gasis introduced through the gas inlet (not shown here, but substantiallythe same configuration as that shown in FIG. 1 a ).

The amount of oxygen introduced into the chamber may be reduced in someother examples if distinct regions of lithium oxide and cobalt oxide arepresent in targets 304, 303, and the oxygen content in such targets maybe sufficiently high in some examples such that no additional oxygen gasneed be introduced into the chamber 322 at all.

FIG. 3 b is a view looking from the drum towards the targets. FIG. 3 cis a cross-sectional view that includes sections of the first target304, the second targets 303 and the substrate 328 on the drum 334.

It will be seen that in FIG. 3 c (the view of the cross-section) thefirst target 304 is angled relative to each of the second targets 303.

In performance of the method, the plasma generated is used to sputtermaterial from the first target and from the second targets onto thesubstrate.

As shown in FIG. 3 d , elemental lithium material has a lower sputteryield than cobalt as measured in atoms yielded per ion received at thesurface at a given energy (less than half at 10 keV). As such, the(negative) potential applied to the first target has a magnitude greaterthan the potential applied to the second targets. The first target alsohas a slightly larger surface area exposed to the plasma than the sumarea of the second targets. As such, the number of ionised Li atomsarriving at the substrate per unit is substantially the same as thenumber of ionised Co atoms arriving at the substrate per unit. Ionisedoxygen atoms are also present as are electrons from the plasma. The highenergy particles made possible by the remote plasma allows forcrystalline LiCoO₂ material, having a hexagonal crystal structure, to beformed in situ on the surface of the substrate.

A greater number of high energy particles from the plasma are receivedat the first target 304 (over the whole surface area of the target) thanat the second targets 303 (summed over the whole surface area of bothsecond targets).

FIG. 3 e shows a schematic cross-section through a further example of anapparatus in accordance with a fourth example, similar to that shown inFIGS. 3 a to 3 c , but in which the targets move and are arranged inpairs, circumferentially around the drum 334. Each pair of targets (i.e.each assembly 302) is arranged to be angled to face towards a locationvery near to the substrate on the drum. Each pair 302 comprises a firsttarget 304 of elemental lithium and a second target of elemental cobalt303. The targets are all positioned at a working distance of about 15 cmfrom the substrate, the working distance being the shortest separationtherebetween. The theoretical mean free path of the system (that is, theaverage distance between collisions for an ion in the plasma) is about20 cm. For each pair of targets (302), in use there is a first plume ofparticles from the first target (304) and a second plume of particlesfrom the second target (303) which converge at a region proximate to thesubstrate. The centre of rotation of the main drum 334 is also thecentre of rotation of the targets. The targets move with an angularvelocity about the centre of rotation slower than the drum. Targets maybe replaced when they have moved out of the plasma on a rotating basis,thus allowing for constant deposition of material on the movingsubstrate.

An example of a battery cathode made in accordance with the secondexample will now be described with reference to FIGS. 4 a, 4 b and 5 a .The substrate 428, 528 comprises a current collecting layer 429, 529, inthis case, a layer of platinum, on which a layer of LiCoO₂ 442, 542 isdeposited. In other examples, another inert metal is used as a currentcollecting layer, for example gold, iridium, copper, aluminium ornickel. In yet further examples, the current collecting layer may becarbon based. In some examples, the current collecting layer is surfacemodified, and in some examples, the current collecting layer comprisesrod-like structures.

As shown on the Scanning Electron Microscope (SEM) image of FIG. 4 a(cross sectional view of a first sample deposited film) and FIG. 4 b(bird's-eye view a second sample deposited film), the LiCoO₂ film layer442, 542 of both samples is polycrystalline in nature. The batterycathodes of FIGS. 4 a, 4 b and 5 a can also be made in accordance withthe methods of the third or fourth example.

A method of making a cathodic half-cell in accordance with a fifthexample will now be described with reference to FIG. 5 a (a firstsample), FIG. 5 b (a second sample), and FIG. 5 c . The method,generally described by reference numeral 3001, comprises depositing 3002a battery cathode material 542 onto a substrate (which in this examplecomprises a current collecting layer 529), and depositing 3003 onto saidbattery cathode material 542 battery electrolyte material 544. In thisexample, the material deposited for the electrolyte 544 is lithiumphosphorous oxy-nitride (LiPON). In other examples, the materialdeposited is another suitable electrolyte material. In some samples ofthe fifth example of the invention (such as the second sample), thehalf-cell may comprise an electrode material 544, and in other samplesof the fifth example, the half-cell may not comprise an electrodematerial 544 (such as the first sample).

In this example, the LiPON is deposited in substantially the same way asthe ABO₂ materials in the first, second, third or fourth examples, usinga remotely-generated plasma. However, in this example, the targetmaterial used is Li₃PO₄, with deposition occurring in a reactivenitrogen atmosphere. In other examples, the target assembly may includea number of targets, with distinct regions of lithium and/or phosphorouscontaining compounds, elemental lithium, or lithium oxide. In otherexamples, the deposition additionally occurs in a reactive oxygenatmosphere.

An example of a method of making a solid-state battery cell inaccordance with a sixth example will now be described with reference toFIG. 6 . The method is denoted generally by reference numeral 5001 andcomprises making 5002 a cathodic half-cell in accordance with the fifthexample (for example, as described above with reference to FIGS. 5 b and5 c ) and contacting 5003 said cathodic half-cell with an anode. In thisexample, the anode is deposited by a convenient method, including remoteplasma sputtering, magnetron sputtering, CVD etc. In other examples, theanode is deposited by thermal evaporation, e-beam evaporation, pulsedlaser deposition, or simple DC-sputtering.

An example of a method of making a solid-state battery in accordancewith a seventh example will now be described with reference to FIG. 7 a. The method is denoted generally by reference numeral 6001 andcomprises making 6002 a plurality of cathodic half-cells of a solidstate thin film battery, making 6003 a plurality of anodic half cells ofa solid state thin film battery and bringing 6004 said cathodic andanodic half cells into contact with one another, thereby forming atleast one battery. A battery so made according to a first sample of theseventh example of the present invention is shown schematically in FIG.7 b . Referring to FIG. 7 b , 628 and 628′ are substrate materials, 629and 629′ are current collecting layers, 642 is the cathode material, inthis case, LiCoO₂, and 644 is LiPON, which acts as both electrolyte andanode.

Alternatively, in other examples the current collector material acts asan anode material. Alternatively, in a second sample of the seventhexample of the invention a further anode material may be deposited. Thisis shown schematically in FIG. 7 c . Referring to FIG. 7 c , 628 and628′ are substrate materials, 629 and 629′ are current collectinglayers, 642 is the cathode material, in this case, LiCoO₂, 644 is LiPON,which acts as electrolyte, and 646 is a suitable anode material.

An example of a method of determining an optimum working distance for aremote plasma deposition system configured for the deposition of layeredoxide materials in accordance with an eighth example will now bedescribed with reference to FIG. 8 a . The method is generally describedby numeral 7001 and comprises:

-   -   Selecting 7002 a range of working distances, wherein a working        distance within said range is +/−50% of the theoretical mean        free path of the system,    -   for a number of test specimens, for each respective specimen,        performing 7003 the method of depositing material according to        the first example at different working distances within the        selected range,    -   performing 7004 a characterisation technique capable of        determining a characteristic feature of a layered oxide        structure on each of the test specimens after deposition has        occurred,    -   identifying 7005 specimens where said characteristic property is        present;    -   from those specimens, selecting 7006 the specimen wherein the        (normalised) intensity of said characteristic peak is highest,        and subsequently selecting 7007 the working distance for the        system to that which was used during deposition of said test        specimen.

In this eighth example, the characterisation technique used is X-raydiffraction, and the characteristic property is a diffraction peak orseries of diffraction peaks. FIG. 8 b shows a number of X-Raydiffraction patterns recorded of films deposited at different workingdistances. From the top diffraction pattern to the bottom diffractionpattern the working distances were 5 cm (731), 8 cm (733), 12 cm (735)and 15 cm (737), respectively. As can be seen from the figure, a workingdistance of 8 cm shows the highest intensity peak 733 at 19 degrees2theta (which is one of the required peak positions 739 for hexagonalLiCoO₂, this particular peak not being present in cubic or spinelstructures of LiCoO₂). Therefore, in this example, 8 cm is chosen as theworking distance. In other examples, a different characterisationtechnique may be used other than X-Ray diffraction. The intensity of thediffraction pattern 731 measured for a working distance of 5 cm is lessintense at 19 degrees 2theta than the diffraction pattern 733 at aworking distance of 8 cm. The diffraction patterns collected for aworking distance of 12 cm 735 and 15 cm 737 do not show thecharacteristic peak for hexagonal LiCoO₂ at 19 degrees 2theta at all.

In some examples, the test specimens of the method are replaced with anaverage value for a number of test specimens, comprising a number oftest specimens, wherein the method of the first example has beenperformed a number of times at the same working distance, and an averagetaken. In some examples the method may be performed a number of timessuch that a range of optimal working distances can be found foroperating the system.

FIG. 9 a shows a sample formed in accordance with the first example,during performing the method of the eighth example, and shows a damagedsubstrate surface (with undesirable oxides) which forms due to thedeposition when the working distance is too short. In this example, theworking distance was 5 cm, and the material deposited was LiCoO₂. As canbe seen from the figure, crystallites have not formed over the wholesubstrate surface, and deformation of the substrate can be seen. Inaddition, regions of Co(II)O, an undesirable phase of cobalt oxide, canbe seen forming on the substrate at this working distance. This isconfirmed by the spectra as shown in FIG. 9 b , which shows peaksrelating to Co(II)O phases (identified at two values 843 of 2theta)being detected in a diffraction pattern 831 obtained for a sample atwhich the working distance was 5 cm, in addition to hexagonal LCO, peaks(identified at 5 values 839 of 2theta). A structural refinement model831′ containing both hexagonal LiCoO₂ and Co(II)O phases, was obtainedfrom the collected diffraction pattern of 831. The difference betweenthe diffraction pattern 831 and the refinement model 831′ is illustratedby the difference line 841. Thus, during the method of the eighthexample, overly short working distances cannot be selected as theoptimum working distance.

An example of a method of determining an optimum range of workingpressures for a remote plasma deposition system configured for thedeposition of layered oxide materials in accordance with a ninth examplewill now be described with reference to FIG. 10 a . The method isgenerally described by numeral 8001 wherein the method comprises:

-   -   Selecting 8002 an initial range of working pressures, from        0.00065 mBar to 0.01 mBar (and optionally from 0.001 to        0.007mBar),    -   for a number of test specimens, for each respective specimen,        performing 8003 the method of depositing material according to        the first example at different working pressures within the        selected range,    -   performing 8004 a characterisation technique capable of        determining a characteristic property of a layered oxide        structure on each of the test specimens after deposition has        occurred,    -   selecting 8005 the test specimen which was deposited at the        lowest working pressure from the group of test specimens which        display a characteristic feature of a layered oxide material,        and setting 8006 this working pressure as the lower bound of the        range,    -   selecting 8007 the test specimen which was deposited at the        highest working pressure from the group of test specimens which        do not show observable signs of damage to the substrate, and        setting 8008 this working pressure as the higher bound of the        range.

In this ninth example, the characterisation technique used is X-raydiffraction, and the characteristic feature is a feature comprises acharacteristic X-Ray diffraction peak of a layered oxide material. FIG.10 b shows an example X-Ray spectra showing how below a certain workingpressure, this characteristic feature is not present. In this example,the presence of a peak at 19 degrees 2theta in the pattern 947 for thesample deposited at 0.0046mBar resulted in the formation of a hexagonalcrystalline phase, whereas the pattern 945 for the sample deposited at0.0012mBar did not lead to the formation of a hexagonal crystallinephase, as shown by the absence of the peak. In other examples, acharacterisation technique may be used other than X-Ray diffraction.

In further examples, the test specimens of the method are replaced withan average value for a number of test specimens, comprising a number oftest specimens wherein the method of the first example has beenperformed a number of times at the same working pressure, and an averagetaken.

In some examples, the method also comprises selecting the optimumworking pressure of the system within the desired range. In thisexample, the optimum working pressure is the working pressure within therange that results in the highest deposition rate.

An example of a method of determining the crystallite size fordeposition of layered oxide materials in accordance with a tenth examplewill now be described with reference to FIG. 11 a . The method isgenerally described by numeral 9001 wherein the method comprises:

-   -   selecting 9002 an initial range of working pressures, from        0.00065 mBar and 0.01 mBar,    -   for a number of test specimens, for each respective specimen,        performing 9003 the method of depositing material according to        the first example at different working pressures within the        selected range,    -   performing 9004 a characterisation technique capable of        determining the crystallite size of each film for each of the        test specimens after deposition has occurred,

The selected range of working pressures may be from 0.001 to 0.007 mBar,for example.

FIG. 11 b is a graph showing, after performing the method of the tenthexample over a given range of working pressures, for a working distanceof 16 cm, that the range of crystallite size that forms for a number offilms deposited in accordance with the first example at differentworking pressures between 0.001 mBar and 0.0065 mBar, is relativelybroad in comparison to FIG. 11 c.

FIG. 11 c is a graph showing, after performing the method of the tenthexample over a given range of working pressures, for a working distanceof 8.5 cm, that the range of crystallite size that forms for a number offilms deposited in accordance with the first example at differentworking pressures between 0.001 mBar and 0.0065 mBar is relativelynarrow in comparison to FIG. 11 b.

It is beneficial to have a narrow distribution of crystallite sizes, asthis makes the crystallite size of films deposited on an industrialscale both predictable and repeatable.

An example of a method of depositing a material on a substrate inaccordance with an eleventh example of an example will now be describedwith reference to FIG. 12 . The method is generally described by numeral1101 and comprises:

-   -   generating 1102 a plasma remote from a plasma target or targets        suitable for plasma sputtering,    -   exposing 1103 the plasma target or targets to the plasma,        thereby generating sputtered material from the target or        targets,    -   depositing 1104 the sputtered material on a first portion of the        substrate.

The method of depositing material on a substrate as described by theeleventh example comprises all of the features of the deposition of thefirst example, although in this example, the target material may be anymaterial. In this example, the target material is crystalline, howeverin other examples the deposited material may take a semi-crystallineform, or be amorphous.

Also presented is a twelfth example, which relates to a method ofmanufacturing a component for an electronic device comprising asubstrate, which will now be described with reference to FIG. 13 . Themethod is generally described by numeral 1201 and comprises depositing1202 a material onto the substrate using a method of the as described inthe eleventh example. The method of the eleventh example in this exampleis performed a plurality of times 1203 in order to deposit multiplelayers. In this example, at least some of the multiple layers may aresemi-conducting layers. In this example, the method is therefore amethod of manufacturing a semi-conducting device or part thereof. Inthis example adjacent layers are be deposited with differing parametersand/or target materials used for the deposition of each layer, in orderto produce an electronic device. In other examples, multiple layers of aplurality of layers of material are deposited with substantially thesame target materials and parameters.

In this example, the substrate comprises one intermediate layer, whichmay optionally act as a current collecting layer. In other examples,there are more intermediate layers, which help with adhesion duringdeposition steps. In some other examples, there is no intermediatelayer. The deposition of the intermediate layer onto the substrate is beperformed in accordance with the method as described in the eleventhexample. In other examples, deposition of the intermediate layer ontothe substrate is performed by another appropriate deposition technologysuch as sputtering, thermal evaporation, electron beam evaporation,pulsed laser deposition, or other thin film deposition technology.

In this example, the method comprises depositing a first semiconductinglayer of material. In this example, the first semiconducting layer isdeposited onto an intermediate layer of material. In other examples, thefirst semiconducting layer is deposited directly onto the substrate. Inthis example, the first semiconducting layer comprises silicon. In otherexamples, the first semiconducting layer comprises aluminium, and insome further examples, gallium nitride. In examples where thesemiconducting layer of material is gallium nitride, the depositionoccurs under a reactive nitrogen atmosphere. In this example, the firstsemiconducting layer of material is doped n-type. This is achieved inthis example by sputtering of a target comprising a compound containingphosphorous. In other examples, this is achieved by use of a differentdopant such as arsenic, antimony, bismuth or lithium. In some furtherexamples, the semiconducting layer of material is doped p-type, withdopants such as boron, aluminium, gallium or indium. In furtherexamples, the semiconducting layer of material is not doped, and is anintrinsic semi-conductor. In some of these examples, the dopant materialis not introduced as a target which can be sputtered, and is insteadintroduced as a gas after deposition, such that the dopant diffuses intothe surface of the semiconducting layer.

In this example, the method comprises depositing a second semiconductinglayer of material, onto the first semiconducting layer of material. Inother examples, the second semi-conducting layer of material isdeposited directly onto the substrate or the intermediate layer (ifpresent). In this example, the second semiconducting layer of materialis an intrinsic semiconductor. In this example, the secondsemiconducting layer of material is gallium nitride. In furtherexamples, the second semiconducting layer of material is doped n-typewith dopants such as phosphorous, arsenic, antimony, bismuth or lithium.In some further examples, the second semiconducting layer of material isdoped p-type, with dopants such as boron, aluminium, gallium or indium.In some of these examples, the dopant material is not introduced as atarget that can be sputtered, and is instead introduced as a gas afterdeposition, such that the dopant diffuses into the surface of thesemiconducting layer.

In this example, the method comprises depositing a third semiconductinglayer of material. In this example, the third semiconducting layer isdeposited onto the second semi-conducting layer of material. In otherexamples, the third semiconducting layer is deposited directly onto thefirst semiconducting layer, second semiconducting layer, theintermediate layer or the substrate. In this example, the thirdsemiconducting layer comprises silicon. In other examples, the thirdsemiconducting layer comprises aluminium, and in some further examples,gallium nitride. In some examples where the semiconducting layer ofmaterial is gallium nitride, the deposition occurs under a reactivenitrogen atmosphere. In this example, the third semiconducting layer ofmaterial is doped p-type. This is achieved in this example by sputteringof a target comprising a compound containing boron. In other examples,this is achieved by use of a different dopant such as aluminium, galliumor indium. In some further examples, the third semiconducting layer ofmaterial is doped n-type, with dopants such as phosphorus, arsenic,antimony, bismuth or lithium. In further examples, the thirdsemiconducting layer of material is not doped, and is an intrinsicsemi-conductor. In some of these examples, the dopant material is notintroduced as a target, which can be sputtered, and is insteadintroduced as a gas after deposition, such that the dopant diffuses intothe surface of the semiconducting layer.

The method of this example may therefore be used to form a p-n or p-i-njunction.

In this example, no further dopants are introduced into some of thesemiconducting layers hitherto described. In some examples, germanium isintroduced as a dopant in the first, second and/or third layers.Germanium alters the band gap of the electronic device, and improves themechanical properties of each semiconducting layer of material. In someexamples, nitrogen is introduced as a dopant in the first, second and/orthird layers of material. Nitrogen is used to improve the mechanicalproperties of the semiconducting layers formed.

Also presented is a thirteenth example, which relates to a method ofmanufacturing a crystalline layer of Yttrium Aluminium Garnet (YAG),which will now be described with reference to FIG. 14 . The method isgenerally described by numeral 1301 and comprises using the method asdescribed in the eleventh example 1302, wherein the YAG is doped 1303with at least one f-block transition metal.

In this example, the dopant material is a lanthanide.

In this example, the dopant material comprises neodymium. In otherexamples, the dopant material comprises chromium or cerium in additionto neodymium. In this example, the crystalline layer of materialcomprises 1.0 molar percent neodymium. In some examples, the materialalso comprises 0.5 molar percent cerium.

In yet further examples, the dopant material comprises erbium. In thisexample, the dopant material is provided as a target, and sputtered asdescribed in the eleventh example. The crystalline layer of material inthis further example comprises 40 molar percent erbium. In one example,the crystalline layer of material comprises 55 percent erbium.

In yet further examples, the dopant material comprises ytterbium. In oneof these examples, the crystalline layer of material comprises 15 molarpercent ytterbium.

In yet further examples, the dopant material comprises thulium. Infurther examples, the dopant material comprises dysprosium. In furtherexamples, the dopant material comprises samarium. In further examples,the dopant material comprises terbium.

In yet further examples, the dopant material comprises cerium. In someexamples where the dopant material comprises cerium, the dopant materialalso comprises gadolinium.

In some examples, instead of the dopant material being provided as adistinct region of a target or targets, the dopant material is, at leastin part, introduced after the deposition of the layer of crystallinematerial, by providing the dopant material as a gas, such that itdiffuses into the layer of crystalline material.

According to a fourteenth example, a method of manufacturing a lightemitting diode is presented, which will now be described with referenceto FIG. 15 . The method is generally described by numeral 1401 andcomprises performing the method according to the twelfth example 1402,and thereafter or therein performing the method according to thethirteenth example 1403, in the case where the dopant used during themethod of the thirteenth example comprises cerium 1404. The layer ofcerium-doped YAG is used as a scintillator in an LED in this example.

The methods according to the twelfth and thirteenth examples may beperformed inside the same process chamber.

According to a fifteenth example, a method of manufacturing a permanentmagnet is presented, which will now be described with reference to FIG.16 . The method is generally described by numeral 1501 and comprisescomprising performing the method according to the eleventh example 1502,wherein the distinct regions of the target or targets provided compriseneodymium, iron, boron and dysprosium 1503, and the method comprisesprocessing the film 1504 such that the layer of material becomes apermanent magnet.

In this example, the final layer of material comprises 6.0 molar percentdysprosium. In further examples, the molar percentage of dysprosium isless than 6.0.

The high target utilisation that the current method provides isbeneficial when constructing electronic devices from rare elements suchas dysprosium. Dysprosium is available in limited Earth abundancy, andso a deposition system with a high target utilisation results in lessmaterial waste.

According to a sixteenth example, a method of manufacturing a layer ofIndium Tin Oxide (ITO) is presented, which will now be described withreference to FIG. 17 . The method is generally described by numeral 1601and comprises performing the method according to the eleventh example1602, wherein the distinct regions of the targets provided compriseindium and tin 1603. The layer of ITO is deposited in such a way that itdirectly forms a transparent crystalline layer of material on deposition1604 onto the substrate. In other examples, a composite target is used,which comprises both indium and tin. In yet further examples, thecomposite target comprises an oxide of indium and tin. The number oftargets used thus may differ in further examples, and a single targetmay be used.

In yet further examples the targets may comprise an oxide of indium, oran oxide of tin. The deposition process in further examples comprisesproviding oxygen, such that the sputtered material from the targetsreacts with the oxygen in order to form Indium Tin Oxide on thesubstrate.

According to a seventeenth example, not separately illustrated, a methodof manufacturing a photovoltaic cell is presented. In this example, themethod further comprises the deposition of an ITO, as described in thefifteenth example In further examples, no layer of ITO is deposited. Inthis example, the method also comprises the deposition of a layer ofperovskite material in between a n-type doped layer of semiconductingmaterial and a p-type doped layer of semiconducting material. Theperovskite layer of material is in this case deposited as described bythe method of the eleventh example. In further examples, it is depositedby another suitable means such as physical vapour deposition, or wetchemistry techniques. In further examples, no perovskite layer ofmaterial is deposited.

In alternative examples, the method comprises the deposition of a layerof copper indium gallium selenide in accordance with the eleventhexample. The copper, indium, gallium, and selenide is provided asdistinct regions of the target or targets. In this example the copper isprovided as an elemental target, and the indium, gallium, and selenideare provided as oxide targets. Other combinations of oxide, elemental,compound or composite targets are used in further examples. The numberof targets used thus may differ in further examples, and a single targetmay be used.

In some examples, the method comprises the deposition of a layer ofcadmium sulphide in accordance with the eleventh example. In thisexample, the cadmium and sulphide are provided as distinct regions ofthe targets in oxide form. Other combinations of oxide, elemental,compound or composite targets are used in further examples. The numberof targets used thus may differ in further examples, and a single targetmay be used.

In some examples, the method comprises deposition of a layer of cadmiumtelluride in accordance with the eleventh example. The cadmium andtelluride is provided as distinct regions of elemental targets in tisexample. In other examples, the cadmium and telluride is provided asdistinct regions of the target or targets in elemental, an oxide, acomposite or any combination thereof. The number of targets used thusmay differ in further examples, and a single target may be used.

Whilst the forgoing description has been described and illustrated withreference to particular examples, it will be appreciated by those ofordinary skill in the art that the invention lends itself to manydifferent variations not specifically illustrated herein.

Where in the foregoing description, integers or elements are mentionedwhich have known, obvious or foreseeable equivalents, then suchequivalents are herein incorporated as if individually set forth.Reference should be made to the claims for determining the true scope ofthe example, which should be construed so as to encompass any suchequivalents. It will also be appreciated by the reader that integers orfeatures of the invention that are described as preferable,advantageous, convenient or the like are optional and do not limit thescope of the independent claims. Moreover, it is to be understood thatsuch optional integers or features, whilst of possible benefit in someembodiments of the invention, may not be desirable, and may therefore beabsent, in other embodiments.

1. A method of manufacturing a crystalline layer of material on asurface, the crystalline layer comprising lithium, at least onetransition metal and at least one counter-ion, wherein the methodcomprises the following steps: generating a plasma using a remote plasmagenerator, plasma sputtering material from a first target comprisinglithium onto a surface of or supported by a substrate, there being atleast a first plume corresponding to trajectories of particles from thefirst target onto the surface, and plasma sputtering material from asecond target comprising at least one transition metal onto the surface,there being at least a second plume corresponding to trajectories ofparticles from the second target onto the surface, wherein the firsttarget is positioned to be non-parallel with the second target, whereinthe first plume and the second plume converge at a region proximate tothe surface of or supported by the substrate, and wherein thecrystalline layer is formed on the surface at said region.
 2. The methodaccording to claim 1, wherein more plasma energy is received at thefirst target than at the second target.
 3. The method according to claim1, wherein the first target faces towards the substrate in a firstdirection, and the second target faces towards the substrate in a seconddirection, the first and second directions converging towards thesubstrate.
 4. The method according to claim 3, wherein the notional lineparallel to the first direction which extends from the centre of thesurface of the first target intersects, in the cross-section, thenotional line parallel to the second direction which extends from thecentre of the surface of the second target, at a location closer to thesubstrate than to either of the targets.
 5. The method according toclaim 4, wherein the location of the intersection is closer to thesubstrate than half of the shortest distance from either of the targetsto the substrate.
 6. The method according to claim 1, wherein at leastone of the substrate and the first and second targets are moving ascrystalline layer is being formed on the surface.
 7. The methodaccording to claim 1, wherein the substrate has a radius of curvature atthe region at which the first plume and the second plume converge andthe targets are arranged circumferentially around the centre of theradius of curvature.
 8. The method according to claim 1, wherein atleast part of the substrate is carried by a rotating drum.
 9. The methodaccording to claim 1, wherein the working distance between the firsttarget and the substrate is within +/−50% of the theoretical mean freepath of the system.
 10. The method according to claim 1, wherein theworking distance between the first target and the substrate is from lcmto 50 cm.
 11. The method according to claim 1, wherein the surfacesfacing the substrate of the first and second targets are planar.
 12. Themethod according to claim 1, wherein plasma is shaped to form a sheet ofplasma that extends in a direction along the width of the substrate andin a direction along the length of the substrate.
 13. The methodaccording to claim 1, wherein the second target comprises at least onetransition metal selected from the group consisting of Fe, Co, Mn, Ni,Ti, Nb, Al and V.
 14. The method according to claim 1, wherein thesubstrate has a thickness of from 0.1 to 10 μm.
 15. The method accordingto claim 1, wherein the crystalline layer formed on the surface has athickness of from 0.001 to 10 μm.
 16. The method according to claim 1,wherein the steps of sputtering material onto the surface are soperformed that the maximum temperature reached at any given time by anygiven square of substrate material having an area of 1 cm², as measuredon the surface opposite to said surface on which the material isdeposited and as averaged over a period of 1 second, is no more than 500degrees Celsius.
 17. A method of manufacturing an electronic componentincluding forming a multilayer sheet of different materials, integratingthe multilayer sheet or a part thereof in an electronic product, whereinat least one of the layers of the sheet is a crystalline layer ofconducting or semiconducting material made by performing the method ofclaim
 1. 18. The method according to claim 17, wherein the substrate isretained as a part of the electronic component.
 19. The method accordingto claim 18, wherein the electronic component is a battery, a functionallayer of a battery, an energy storage device or a cell of battery.
 20. Abattery comprising one or more layers of crystalline material formed byperforming the method according to claim
 1. 21. A battery comprisingmultiple stacked cathode layers, multiple stacked electrolyte layers,and multiple stacked anode layers, wherein at least two of the multiplestacked cathode layers are made by performing the method according toclaim 1.